Characterization of V. cholerae O1 biotype El Tor serotype Ogawa possessing the ctxB gene of the classical biotype isolated from well water associated with the cholera outbreak in Kerala, South India.

P S Reethy,K V Lalitha

doi:10.2166/wh.2021.263

Abstract

We investigated 22 water samples (17 well water and five pipe water - both chlorinated) and six soil samples from the surroundings of wells of the households of suspected patients from Palakkad district, Kerala (India), from where a cholera outbreak was reported during June-July 2016. A total of 25 Vibrio cholerae isolates were collected from three well water samples during a recent cholera outbreak. Biochemical and serological studies revealed that all of the isolates belonged to serogroup O1, biotype El Tor, serotype Ogawa. PCR assays confirmed the occurrence of ctxB, ctxA, hlyA, tcpA El Tor,VPI, ace, zot, ompW, rfbO1 and toxR genes in all isolates. The presence of the ctxB gene of the classical biotype in all of the El Tor isolates suggests that it is a new variant of El Tor biotype. Antibiogram profile of all V. cholerae O1 isolates revealed resistance towards five classes of antibiotics island and indicates that they were multidrug resistant. ERIC-PCR and PFGE finger prints showed the clonal relationship among the V. cholerae O1 isolates. The results of this study revealed the emergence of a new variant of El Tor biotype in the water samples from Palakkad district, from where a cholera outbreak was reported.

Highlights

Among the 90 presumptive V. cholerae isolated from chlorinated water and soil and characterized biochemically as per FDA protocols (USFDA ), 25 isolates from three well waters were identified as V. cholerae and confirmed using rapid diagnostic kit API 20E
In the earlier cholera outbreaks reported from Alappuzha and Palakkad districts in Kerala, ctxA and tcpA genes were detected in V. cholerae O1 EI Tor Ogawa clinical strains (Radhakutty et al )
The detection of El Tor strains with classical ctxB gene in the environmental V. cholerae O1 in this study as well as in the outbreaks from Chennai and Odissa indicates their wide distribution in the aquatic environment of the Indian subcontinent (Goel et al ; Pal et al )

Summary

Introduction

Cholera is an acute gastrointestinal illness characterized by severe watery diarrhoea and is caused by the bacterium Vibrio cholerae that is acquired by the ingestion of. Cholera alone causes 120,000 deaths annually (Sack et al ). The incidence of cholera is estimated to be 1.6 cases/1,000 population per year or 40/1,000 cases of acute diarrhoea in India (Sharma et al ).

Methods

Results

Conclusion